Fluid extraction arrangement for engine air induction system

ABSTRACT

An engine includes an air induction system for providing air to a plurality of cylinders, an exhaust system for conveying exhaust gas from the cylinders, and a secondary air injection (SAI) system for extracting air from the induction system and injecting the air into the exhaust system to promote exhaust gas oxidation and to heat a catalytic converter. The SAI system extracts air from the induction system through a plurality of holes to evenly distribute the effects of the extraction, thereby reducing velocity gradients and turbulence levels around the mass air flow sensor inside the induction system.

TECHNICAL FIELD

This invention relates to internal combustion engines having a secondary air injection system that extracts air from an air induction system at multiple extraction points to reduce the effect of air extraction in the induction system.

BACKGROUND OF THE INVENTION

Secondary air injection (SAI) systems are used with internal combustion engines to promote oxidation of unburned hydrocarbons and reduce catalytic converter light-off time in the period immediately following engine cold start. SAI systems introduce air extracted from the engine's air induction system to the engine's exhaust system downstream of the exhaust valves, where the air mixes with unburned hydrocarbons in the exhaust and promotes hydrocarbon and carbon monoxide oxidation.

Most prior art SAI systems extract the air they feed into the exhaust system from an extraction point located between the air filter and mass air flow sensor in the air induction system. Since SAI systems generally operate when engine loads are relatively light, the air flow rate through the SAI system can far exceed that which passes through the throttle body and into the engine's intake manifold. Under these conditions, air extraction by the SAI system distorts the air flow velocity field passing through the mass air flow (MAF) sensor located farther downstream from the SAI extraction point. This distortion may introduce uncertainty in the mass air flow rate the MAF sensor determines is entering the engine. Prior art air induction systems may use a software-based correction in the engine calibration to compensate for the influence of SAI system air extraction on the signal produced by the MAF sensor.

SUMMARY OF THE INVENTION

An internal combustion engine includes an air induction system having a manifold and a conduit. The conduit defines an air passageway that is in fluid communication with the manifold. The passageway is configured to convey air from the atmosphere to the manifold, which then distributes the air to a plurality of engine cylinders. An exhaust system has a manifold configured to selectively convey exhaust gas from the cylinders. A secondary air injection system is configured to convey air from the induction system to the exhaust system.

The secondary air injection system is in fluid communication with the conduit through multiple holes formed therein, and is configured to extract air through the multiple holes and inject the air into the exhaust system. The use of multiple holes to extract air from the conduit reduces the influence of the SAI system on mass air flow sensors by minimizing the effect of SAI air extraction on the air flow velocity field inside the induction system. As a result, the uncertainty in MAF sensor readings may be significantly lower than in prior art systems that use a single SAI extraction hole. The use of multiple extraction holes also helps to reduce turbulence levels in the air induction system.

In an exemplary embodiment, the multiple holes are evenly spaced around the circumference of the conduit. A fitting concentrically surrounds the conduit and cooperates with the conduit to define an annular chamber. The annular chamber is in fluid communication with the conduit passageway through the multiple holes.

The above features and advantages, and other features and advantages, of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an internal combustion engine with a secondary air injection system configured to extract air from an air intake conduit and inject the air into an exhaust system; and

FIG. 2 is a schematic, cross-sectional view of a coupling between the secondary air injection system and the air intake conduit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, an internal combustion engine 12 includes an air induction system 16. The air induction system 16 includes an air filter 20 through which air 22 is drawn from the atmosphere and filtered as understood by those skilled in the art. A conduit 24, such as a hose or pipe, defines a passageway (shown at 26 in FIG. 2) that conveys air from the air filter 20 to an intake manifold and plenum 28 for distribution among the engine cylinders 30. A throttle valve (not shown) regulates the amount of air flowing into the manifold and plenum 28.

A mass air flow sensor 32 is operatively connected to the conduit 24 to monitor the mass air flow rate through the conduit 24. The mass air flow sensor 32 transmits signals indicative of the mass air flow rate to an engine control module (not shown). The engine control module uses the data from the mass air flow sensor 32 in the control and monitoring of various engine operating characteristics, as understood by those skilled in the art.

The engine 12 also includes a secondary air induction system 36. The air induction system 36 includes a secondary air injection pump 40 that draws air from conduit 24 into conduit 44 through a coupling 48. Air from conduit 44 is then conveyed through conduit 52 and into the engine's exhaust system 58. The exhaust system 58 includes a manifold 60 with runners 62, which are in fluid communication with the exhaust ports (not shown) of the cylinders 30. The exhaust manifold 60 conveys exhaust gas from the exhaust ports to a catalytic converter 64. The secondary air injection system 36 includes solenoid-operated valves (not shown) to selectively prevent air from flowing from the air induction system 16 into the exhaust manifold 60.

The location in the exhaust system where the secondary air injection system 36 injects air is shown schematically. Those skilled in the art will recognize that it may be desirable for the secondary air injection system 36 to inject air as far upstream in the exhaust system as possible so that the exhaust gas that mixes with secondary air has a sufficiently high temperature. In the context of the claimed invention, the exhaust system includes all conduits downstream of exhaust valves, including exhaust ports (not shown), runners 62, etc. Thus, for example, and within the scope of the claimed invention, a secondary air injection system that is configured to convey air into an exhaust system includes a secondary air injection system that is configured to inject air into exhaust ports formed in a cylinder head.

Referring to FIG. 2, wherein like reference numbers refer to like components from FIG. 1, the conduit 24 is characterized by a generally annular cross-section, and, accordingly, the passageway 26 through which the air flows is characterized by a generally circular cross section. More specifically, the conduit 24 defines an inner surface 66 that defines the passageway 26, and an outer surface 68 opposite the inner surface 66. The conduit 24 defines a plurality of apertures that extend from the passageway 26 to the exterior of the conduit 24 and that are evenly spaced from one-another along the periphery of the conduit 24. More specifically, in the embodiment depicted, the conduit 24 defines four holes or apertures 72A-D that extend radially from the passageway 26 to the exterior of the conduit 24. Since the conduit 24 has an annular cross section, the apertures 72A-D are evenly-spaced circumferentially with respect to the conduit.

Although the embodiment depicted includes four apertures 72A-D, more or fewer apertures may be employed within the scope of the claimed invention. For example, two apertures that are evenly-spaced circumferentially, i.e., that are 180 degrees apart, may be employed. Similarly, three apertures that are evenly spaced circumferentially, i.e., that are 120 degrees apart, may be employed.

The coupling 48 has a generally annular cross section, and concentrically surrounds the conduit 24. The inner surface 76 of the coupling 48 and the outer surface 68 of the conduit 24 cooperate to define a ring-shaped chamber or passageway 78 that is in fluid communication with the passageway 26 via apertures 72A-D, and that is in fluid communication with conduit 44. In the embodiment depicted, the surfaces 66, 68, 76 are characterized by a cylindrical shape and are thus circular in cross section.

Air from the passageway 26 defined by conduit 24 can enter the chamber or passageway 78 defined by the coupling 48 through apertures 72A-D. The air then flows from the passageway 78 to the conduit 44, and through the remainder of the secondary air injection system 36 into the exhaust manifold 60. The chamber 78 is sealed at the axial ends of the coupling 48 to prevent air from leaving the chamber 78 except through conduit 44.

Since air is extracted through multiple holes, especially through multiple holes that are evenly spaced circumferentially around the conduit 24, the effects of air extraction from the conduit are distributed throughout the conduit cross-section, thereby reducing or eliminating air velocity gradients and turbulence levels within the induction system that may be caused by air extraction from a single hole.

While the best mode for carrying out the invention has been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims. 

1. An internal combustion engine comprising: an air induction system including an intake manifold and a conduit defining an air passageway in fluid communication with the intake manifold, said conduit defining a plurality of holes; an exhaust system including an exhaust manifold configured to convey exhaust gas; and a secondary air injection system being configured to convey air from said conduit through said plurality of holes to said exhaust system.
 2. The internal combustion engine of claim 1, wherein said plurality of holes are evenly spaced from one another along the periphery of said conduit.
 3. The internal combustion engine of claim 1, further comprising a coupling concentrically surrounding said conduit and cooperating with said conduit to define a chamber in fluid communication with said secondary air injection system and in fluid communication with said passageway via said plurality of holes.
 4. The internal combustion engine of claim 3, wherein said conduit is generally circular in cross section; and wherein said chamber is generally annularly shaped.
 5. The internal combustion engine of claim 4, wherein said plurality of holes includes at least four holes.
 6. An internal combustion engine comprising: an air induction system including an intake manifold and a conduit; said conduit having an inner surface and an outer surface, said inner surface defining an air passageway in fluid communication with the manifold; said conduit defining a plurality of holes extending from the passageway to the outer surface; an exhaust system including an exhaust manifold configured to convey exhaust gas; and a secondary air injection system being configured to convey air from said conduit to said exhaust system; said secondary air injection system including a coupling surrounding a portion of said conduit and cooperating with said outer surface of said conduit to define a chamber in fluid communication with said holes; said chamber being in fluid communication with said secondary air injection system.
 7. The internal combustion engine of claim 6, wherein said conduit has a circular cross section and wherein said chamber is generally annular.
 8. The internal combustion engine of claim 6, wherein said plurality of holes are evenly spaced circumferentially.
 9. An air intake system for an internal combustion engine with a secondary air injection system, the air intake system comprising: an air filter; an intake manifold; a conduit defining a passageway that provides fluid communication between the air filter and the intake manifold, said conduit defining a plurality of holes being evenly spaced along the circumference of the conduit; and a coupling operatively connectable to the secondary air injection system and cooperating with the conduit to define a chamber in fluid communication with the passageway via the plurality of holes. 